4200 front wishbone bush removal.

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Junior Member

Could someone please advise me as to the safest method of removing the wishbone bushes. Normally I would make a "pot" for the larger end of the bush to sit in. Then press it out from the smaller end. The problem here is that there doesn't appear to be enough metal surrounding the bush for the "pot" to register on. I do not want to ruin the wishbone, that would really spoil my day.

Member

Junior Member

Well it's easy once you know how. They're very easy to fit but a right pain in the posterior to remove. Whoever thought it up deserves a medal. I have to say though that although it's straight forward enough , albeit a right pain it helps if you have a hydraulic press and a lathe to make the press tools.

Member

I discussed the bush replacement briefly whilst at McGtath Maserati last week'
The advice I was given was along the lines of "if they dont appear to be off centtre, and they'd not been presented with a car in which they were knocking, leave them be. And because the risk of cracking them was high. Also that the degradation you see on the flanges/exterior isnt necessarily replicated inside the bushes where they are actually doing the work...'
We all have different comfort levels to risk. And it seems something that McGrath havent actually tried, which reduces the pertinence of the advice to educated conjecture..
Hence the interest in further elucidation..
IIRC, Zep told me it required @10T of hydraulic pressure to get removed...by which point it was a missile!
I bet you could machine them out too if you had access to the right kit?!!

Moderator

In short, you cut the end off the bush, press out the centre, use a grinder with a flap disc to weaken the flange on the top of the bush, then a punch to gently fold it up until you have enough room to put a decent sized press tool onto the face of the wishbone, then put it on the press. Mine we very keen to stay in place, so they made a bang when they moved for the first time, but it only moved a few millimetres to not a missile as such!

The first attachment is the 4200 bush, the second one is a GTS one, to show what the aim is.

As Tim says, this is all about your appetite for risk, it takes a steady hand to do it, and it you are comfortable with it then there is no reason why not. But you do so at your own risk!

As for whether it makes a difference, my car was transformed and the bushes weren't as bad as some I have seen, and I have seen a few now.

Member

In short, you cut the end off the bush, press out the centre, use a grinder with a flap disc to weaken the flange on the top of the bush, then a punch to gently fold it up until you have enough room to put a decent sized press tool onto the face of the wishbone, then put it on the press. Mine we very keen to stay in place, so they made a bang when they moved for the first time, but it only moved a few millimetres to not a missile as such!

The first attachment is the 4200 bush, the second one is a GTS one, to show what the aim is.

As Tim says, this is all about your appetite for risk, it takes a steady hand to do it, and it you are comfortable with it then there is no reason why not. But you do so at your own risk!

As for whether it makes a difference, my car was transformed and the bushes weren't as bad as some I have seen, and I have seen a few now.

That does all seem quite doable...And all done with no heat or penetrant lubrication.....? The problem is the dissimilar metals and welding themselves together, i guess...

Noted, your comments regarding the "feel" of the car following replacement - 15 yr old bushes and 60K miles going to take their toll, im sure
My wish bones definitely dont appear to be "sculpted" like those of the GTS. Whilst they are built up with strengthening "rim" material, the body that accepts the bush is not uniform thickness..I should look closely to see if this is true of all the locations really but Id have to say there is less "meat" around mine from first inspection !

Member

Moderator

That does all seem quite doable...And all done with no heat or penetrant lubrication.....? The problem is the dissimilar metals and welding themselves together, i guess...

Noted, your comments regarding the "feel" of the car following replacement - 15 yr old bushes and 60K miles going to take their toll, im sure
My wish bones definitely dont appear to be "sculpted" like those of the GTS. Whilst they are built up with strengthening "rim" material, the body that accepts the bush is not uniform thickness..I should look closely to see if this is true of all the locations really but Id have to say there is less "meat" around mine from first inspection !

Junior Member

So far I have only pressed out one bush from the LH upper wishbone just to prove the method as described by Zep. The bush came out easily and without undue pressure being applied. Interestingly there was no sign of corrosion which I had half expected to find when two dissimilar metals are in contact for an extended period of time. I have completely stripped down the LH side suspension and will be doing the same to the RH side today and tomorrow. The shock absorber bushes will be replaced as well at the same time. The intention is to have all the steel "bracketery" to which are attached various pipes and wires re plated along with the wheel retaining bolts. The springs and anti roll bar plus a couple of other parts will be powder coated. This hopefully will completely refresh the front end of the car. When I've recovered from this I may very well have a go at the back end of the car.
At this point I have to say that without the help of various members of this forum things would have been more difficult. Other jobs planned for this year include replacing both the main engine cooling radiator and the heater radiator. This however is not the end of the jobs on my list but is enough for the present.
My car is 16 years old with 74000 miles on the clock. It has a service history up to 2014 then nothing until it had a so called service when I bought it in February 2016. Hopefully though it will be in good health once again in the near future.

Centenary Club

Hmm.. not cast but forged, A blank is heated to just shy of molten and is pressed rapidly in a form (mould) at immense pressure hence ‘drop forged’ the spare material is trimmed around the edges giving the look of sand casting. This is actually how the known fault is incorporated at manufacturing as the material is ‘formed’ around the bush mounting points it joins on the reverse, the problem is that the material is not quite moulten and does not fully join or weld, I suspect because of slight oxidisation or slag, dross or other contamination. This over time leads to the splits we have seen.

The advantage over moulding is drop forging aligns the grain of the metal and massively increases the strength.

Moderator

Hmm.. not cast but forged, A blank is heated to just shy of molten and is pressed rapidly in a form (mould) at immense pressure hence ‘drop forged’ the spare material is trimmed around the edges giving the look of sand casting. This is actually how the known fault is incorporated at manufacturing as the material is ‘formed’ around the bush mounting points it joins on the reverse, the problem is that the material is not quite moulten and does not fully join or weld, I suspect because of slight oxidisation or slag, dross or other contamination. This over time leads to the splits we have seen.

The advantage over moulding is drop forging aligns the grain of the metal and massively increases the strength.

Good point Newton, they are probably forged, but they won't be forged around a former for the bushing holes - these will generally be machined into the arm after forming as in the pic below of a formed blank ready for machining. Interestingly the front wishbones seem to be made from the same forging, just machined differently at the same part carries two part numbers

To my understanding there are a couple of theories on why they crack, one is that the bush corrodes and expands, causing the crack to form at the stress concentration point of the forging flash on the inside, or (my personal view) that the inner sleeve of the bush (which is metal on metal with a smear of white grease) seizes over time, which means that as the suspension moves it tries to twist in the arm, causing the crack. Either way everyone should be checking for cracks!

@atreyu1 if your bush came out too easily you might well have a crack forming. I would get some crack detection spray and give it a good coating to see if it highlights any defects before reassembly.

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Beat me to it Zep...
I gleaned from McGrath also that Maserati "revised" the casting to include more material in attempt to stave off failure from the stresses of use..Not sure how accurate that is however...
Im really gong to have to look again at the castings on mine as they are not uniform barrel shaped plugs from memory...